Keith Fulton and Louis Pepe are the directors who gave us Lost in La Mancha, the brilliant documentary about Terry Gilliam's attempt to film Don Quixote. Now they have created an intriguing oddity of a film, based on a 1977 novel by Brian Aldiss, and it isn't right to call it a mockumentary; more a serious documentary about something that does not exist.

Harry and Luke Treadaway play conjoined Siamese twins, Tom and Barry Howe, who are plucked from rural obscurity by a music promoter in the 1970s to become a growing cult in the pub rock scene that spawned punk. (The actors are twins, but not conjoined.) They scream their lyrics over churning guitars and encourage freaky fans to touch the flap of skin that joins them at the chest.

There is something very bizarre about these Howe brothers, a weirdly plausible but entirely imaginary musical phenomenon which, in this parallel universe, inspired punk, new wave, and all the guitar bands which followed. A completely made-up prehistory, and a clever alternative commentary on English pop culture.